Open-yard storage of solids in bulk is used for doal, various ores, and similar bulk solids not susceptible of substantial degradation by normal weather conditions. As in any type of storage system it is normally considered desirable to rotate the stored material, that is to reclaim the material in the order it was stored so that the last material stored is the last material used. This necessitates, of course, reclaiming the material from the bottom of the pile, which in some systems can be several hundred meters long and ten to twenty meters high.
The standard procedure of simply using a crane or the like obviously makes it impossible to rotate the material, as the crane or other such arrangement must take material off the top of the pile. Such an arrangement has the further considerable disadvantage that when the pile is inside a warehouse one must provide sufficient headroom above the pile to allow for movement of the overhead crane or the like.
It is also standard practice to form in the ground underneath the normally elongated pile an underground tunnel made of reinforced concrete. A heavy-duty conveyor belt is provided in this tunnel. Floor gates, such as described in my earlier patent application No. 872,832 filed Jan. 27, 1978 (now U.S. Pat. No. 4,186,854), allow the material to drop through the floor under the pile, which floor is also the roof of the tunnel, onto the conveyor belt. It is also known to provide such floor openings with unloading carriages such as described in my copending application No. 855,270 filed Nov. 28, 1977 (now abandoned).
The disadvantage of this last-described system is that the construction of the underground tunnel is an extremely expensive operation. Furthermore in the event the storage system is no longer needed it is impossible to reuse or employ elsewhere most of the elements of the reclaiming system.